For You, Brother
by Somewhere Nowhere
Summary: Sirius and Regulus switch places, after Sirius finds out Regulus betrayed Voldemort. When Sirius is killed in Regulus' place, the Black heir decides he'll pay back his brother's sacrifice however he can. When James and Lily die, that means taking in Harry Potter, his brother's godson. Can Regulus raise a baby Harry alone? Can he thwart Dumbledore's machinations?
1. Sacrifice

Sirius and Regulus switch places, after Sirius finds out Regulus betrayed Voldemort. When Sirius is killed in Regulus' place, the Black heir decides he'll pay back his brother's sacrifice however he can. When James and Lily die, that means taking in Harry Potter, his brother's godson. Can Regulus raise a baby Harry alone? Can he thwart Dumbledore's machinations?

**July 15, 1981**

Regulus fidgeted nervously and looked around the dingy flat. It was small, takeout containers littering every available surface, only two tiny windows lighting the room. He nearly jumped as the door banged open and turned to face a man he hadn't seen in two years. Sirius was wrapped around a rather buxom brunette. He hadn't even noticed Regulus as he stumbled through the doorway kissing his conquest. If he hadn't been so nervous, Reg probably would have laughed. Typical Sirius. Instead he settled for clearing his throat and taking a couple steps forwards. His brother turned his dark head towards him immediately. "R-regulus?" Sirius extricated himself from his date and squinted towards him. "What the hell are you doing here?" The confusion on the elder Black's face shifted into disgust and Sirius nearly snarled at him. "Get out. I have no business with slimy little snakes."

Regulus flinched at his older brother's tone. The sleazy woman laughed gratingly. "I really need to talk to you Siri." The twenty one year old looked shocked. Reg pressed on. "I need your help. Please Siri, I want out." Dark blue eyes narrowed in suspicion. Reg plastered on his most pleading face. The one Sirius could never say no to when they were little. Sirius sighed and nodded before turning a charming smile on the woman watching them. "Sorry, looks like I have other plans." The woman seemed affronted until Sirius leaned in and whispered something in her ear. With a giggle, she pulled him in for a long kiss, then flounced out the door satisfied.

"So what's this about? Why the sudden change of heart Reg?" Sirius' tone was carefully cold, Regulus recognized it as one their father used when he meant business. Reg took a deep breath and pushed up his left sleeve. "I was marked after graduation. Mother and father were so proud. I was finally living up to their expectations." _The ones you left to get dumped on me, _he added silently. "They made us do…stuff. It was awful Siri. All those people. I- I don't like muggles, but what we had to do…" He trailed off, forcing down those horrible memories. "Then the Dark Lord asked me to help hide something. Something important. I let him borrow Kreacher." Sirius' normally expressive face was blank. "I'm not sure what it is, but I'm positive it's valuable. I could get it." Reg took a deep breath. "I could get it and pass information to you for Dumbledore. Please Siri, I can't do this anymore." To his embarrassment, he felt tears pricking the corners of his eyes. Sirius held himself stiffly, looking so hard at Regulus that the young man wondered for a moment if he had learned legilimancy. Sirius must have found whatever he was looking for, because he relaxed and nodded. "Okay Reg."

**September 8, 1981**

"Siri, he'll be going after the Potters and Longbottoms soon." Regulus winced as Sirius turned deathly pale. "They're under fidelus. He can't find them." Regulus nodded. "He's looking for them though," privately Regulus thought the Dark Lord seemed suspiciously casual regarding the search. It was almost like…but no. James and Lily had Sirius as their secret keeper. There was no way the Dark Lord had gotten any information from him. Yet. "Just be careful Siri." Turning, Regulus apparated back to Grimmauld Place.

**September 23, 1981**

"I-I think he knows Siri!" Regulus trembled as he clutched his brother's robes. "I think he k-knows that I'm s-spying!" Sirius pulled him closer, running a soothing hand over his back. "Don't go back then. You've done enough." Reg felt his chest ache at the gentle concern. "I have to, at least for one more meeting. He's going to name the date for the attack on the Longbottoms and Potters." He knew Sirius felt torn between his safety and his best friend's. He reached up and tugged a lock of Sirius' dark hair with a forced playfulness. "I'll be fine Siri. I've lasted this long." He let his head rest on his brother's chest for another moment. This could be the last chance he had to hug him. As if in confirmation of that thought, his mark began to burn painfully. Regulus pulled away. "I've got to go Sirius." He quickly tugged on the death eater robes he had brought and tugged up his sleeve. As soon as he touched the mark, he'd be taken inside the Dark Lord's wards. He took a last long look at his brother. "Bye Sirius." He brought his hand to the mark. At the last second a heavy weight latched onto him, before he was pulled away to Riddle Manor.

"Sirius!" Regulus looked over at his brother in shock. Sirius had managed to grab him as he disappeared and now both Blacks were in the middle of the Dark Lord's hideout. "What are you doing?!" He hissed, irate that his brother had followed him. Sirius grinned. "I'm not going to let you face the Dark Tosser by your lonesome." Regulus scowled. "You're mad! You'll get us both killed for sure!" Sirius shook his head. "Don't be so certain Reg." The older Black pulled his wand. "Love you Reg." One quick _Petrificus Totalus _later, Regulus Black was laying frozen on the floor, furious and terrified. Sirius stripped off his death eater robes (with a bit of difficulty due to his being petrified) and put them on with a grimace. Pulling a silvery item from some hidden pocket, Sirius draped it over him carefully. _An invisibility cloak? _Sirius grinned at him again. "It's James'. I borrowed it. Make sure to give it back." Sirius winked at him and donned the bone white mask. "See ya little brother."

Hours passed. Suddenly, the petrification on him was broken. _Oh no! Sirius! Sweet Merlin no! _Getting shakily to his feet, Reg adjusted the cloak and crept into the hallway. Voices approached him and he pressed himself into an alcove, listening hard. "Can' t believe Black went traitor. Just like that brother of his." Regulus recognized the speaker as Dolohov. "Yeah," McNair chimed in, "Who would've thought little Regulus would disobey mommy and the Dark Lord?" Regulus winced. "At least the traitor got his!" Reg felt the color drain from his face. _Sirius! _Suddenly the two came into view, dragging a bloody, mangled body behind them. Regulus wanted to puke.

"Avada Kedavra! Avada Kedavra!" Dolohov and McNair fell to the ground with a thump, never seeing their murderer's face. Regulus rushed over to Sirius, tears running down his cheeks. "Siri? Siri?" Reg mumbled over and over, clutching his brother's rapidly cooling body. Tears nearly blinding him, he hauled Sirius over his shoulder, not minding the blood that drenched him. "I'll get you outta here Siri. I promise." He wandered out of the mansion with his brother's body, by some miracle remaining unseen. "Now the apparition clearing isn't too far from here…" He kept up a running commentary, more than a little hysterical and most definitely in shock. He was so sure Sirius would pop back up with that devilish grin and answer back. Regulus let out a bitter sob. Sirius was never going to answer back. It was all his fault.

**October 31, 1981**

Regulus wandered up to the smoking remains of Lily and James Potter's cottage. Faintly he could hear a baby crying. Sirius' godson. _Harvy? Haley? Harry? Yes Harry. _Reg gingerly crept up the damaged staircase. The steps creaked ominously beneath his weight. A few more tense seconds and he was on the second floor. The crying was coming from a room to his right. Walking in, he saw a red haired woman lying motionless on the floor. A few feet away was a pile of black robes and ash. A small dark haired toddler stood in his crib, grasping the bars and wailing. Reg hesitated, then walked over to the woman first. No pulse. Gulping, he shook off his cloak and laid it over her as tenderly as he had covered James with a conjured sheet. Then he turned to the child.

Harry was staring at him with big green eyes, his wailing quieting to small sniffles. The toddler reached out, obviously wanting to be held. Unsure and awkward, Regulus reached into the crib and picked the child up. He winced as Harry snuggled close, wiping his mucus and tears all over. _Ugh. Why do people want kids again? _Ignoring his discomfort, he carefully carried Harry back downstairs and out of the house. Harry was Sirius' godson, and with Sirius and the Potter's dead Regulus had no idea who the child would go to next. Well he wouldn't let anyone else take his responsibility. Sirius had died for him. All of Siri's responsibilities were now his. With that thought firmly in mind. Regulus pulled up the hood of his cloak and made sure Harry was covered and warm. Humming softly to himself, he took one last look at the cottage and strolled gracefully down the street.


	2. Not Your Padfoot

**Disclaimer: I don't own Harry Potter.**

**October 31, 1981**

**(Godric's Hollow)**

Albus Dumbledore looked at the ruined cottage sadly. James and Lily were dead, Alice and Frank were in St. Mungos, and little Harry Potter was missing. Peter Pettigrew had been discovered as a traitor thanks to Severus. He confessed under veritaserum to being the Potter's secret keeper and selling them out to Voldemort. By the time the Order had reached Godric's Hollow though, it was too late. Albus sighed. Voldemort was not completely gone. They needed Harry. His one hope was that Sirius Black, who had been missing since September, might have taken Harry with him.

(**A small flat in muggle London)**

Regulus transfigured a chair into a crib. Placing the half asleep toddler in it, he yawned and sank onto the living room's narrow couch. "What now Siri?" Reg found himself staring into his reflection in the room's small window. He looked like Sirius. If it wasn't for the slight age difference, they could probably pass as twins. Same eyes, hair, nose, and lips. Reg had always been a little shorter, but only by about two inches or so. He touched his cheek pensively. "You should be here you know. You should be the one sitting here, taking care of this kid Siri." His reflection stared back at him silently. Regulus sighed and looked away, his fingers going to the silver chain he had transfigured from Sirius's ashes. The familiar guilt he had felt in the weeks since Sirius' death bubbled back to the surface. "It should've been me. It should've been me not Sirius damn it!" He sank to his knees, his hands sinking into his hair painfully. "Shoulda been me." Hot tears were spilling down his cheeks.

"P'foot!" Harry's voice made him scrub at his eyes and look up. "P'foot!" The toddler repeated insistently, waving his chubby arms at Regulus. The Black heir stood with a sigh and walked over to the crib. "What?" He asked, then felt stupid for doing so. Harry was just a year old after all. "P'foot!" Regulus picked the child up and looked down at the green eyes. "I don't understand what you're saying." Harry giggled and pulled on Regulus' hair. "Ow! Let go you little…" Harry looked up at him with tears starting to form, his lower lip quivering pitifully. Reg fought down his panic and gently bounced the baby like he'd seen his cousin Narcissa do with Draco. "There there. I'm sorry. I didn't mean it." Regulus felt like he'd start crying himself if the kid started sobbing. Luckily, the words and soothing movement seemed to do the trick. The tears disappeared and Harry started babbling contentedly. "P'foot." Suddenly Regulus was struck with a memory.

_He was walking on the grounds of Hogwarts near the lake. Laughing caught his attention. Of course it was his idiot brother and his sidekicks. Sirius was laughing at something Potter had said, Lupin was shaking his head at the two. Sirius didn't even spare him a glance as they passed close by. Angry, Regulus turned to go back into the castle. "Padfoot, wasn't that your brother?" He had heard James Potter ask behind him. _

"Padfoot," he whispered. He looked down at Harry. "You think I'm Sirius." Harry just giggled and patted his cheek, green eyes lit up with excitement. "P'foot!" Regulus gave him a small sad smile. "No Harry. I'm not your Padfoot." He hugged the little boy closer. "I wish I was though." With Harry in his arms, he settled back on the couch. The little body in his arms was warm. He felt Harry nuzzle his face against his chest. He wasn't alone. He didn't have Siri anymore, but he wasn't alone. Running a hand through the child's dark, baby fine hair Reg relaxed. He would take care of Harry like Sirius would have done. His expression darkened. He would also find a way to get to Peter Pettigrew. Oh he knew who had betrayed the Potter's whereabouts and who had told the Dark Lord that someone was leaking important information to the Order. Pettigrew had gotten Sirius killed. Regulus smiled unpleasantly. Pettigrew would pay, he would make sure of it. Harry shifted, and Regulus realized he had fallen asleep. Placing the baby back in his crib as gently as he could, he went and climbed into the lumpy bed that had come as part of the flat's furnishings. Tomorrow, he would start looking for a better place to live, after all he couldn't take Harry back to Grimmauld with his mother there. Running over everything he needed to do in the morning, Reg gradually fell asleep.

**(Hogwarts)**

"Severus, we must find Harry at all costs." Albus Dumbledore peered at the pale potions master from behind his desk. The young man had deep shadows under eyes red from crying. He was taking Lily's death hard. Albus' gaze softened in pity. "I'm sorry for your loss my boy." Severus Snape nodded mechanically and stared at his clenched fists. He could feel his nails drawing blood from his palms. It pleased him. Lily was dead. He deserved much worse punishment than bloodied hands. "He has her eyes you know," the headmaster said trying to get a reaction. Severus' head snapped up. "Will you help me find him?" The dark gaze studdied the old man for several long seconds. Severus cleared his throat. "I will." _And once I find him I'll protect him. Even from you, _the former death eater thought fiercely. _For Lily. _

_A/N: Just an idea I had. I haven't seen many stories with Regulus in them. Let me know what you think :)_


	3. Day One

**November 1, 1981**

Regulus groaned as he dragged himself off the lumpy mattress. Harry was crying again. He cast a quick tempus and bit back a curse. _Three in the bloody morning! _Taking a deep, calming breath he walked over to the transfigured crib. Harry was sitting up, his little face red and unhappy. Tears poured down his cheeks and his big green eyes stared up at Regulus pleadingly. With a sigh, the former death eater lifted the child carefully. "What's wrong now?" Harry had gotten him up once earlier for a diaper change. A quick check assured the frazzled man that wasn't the current issue. _Thank Merlin._ He held the baby helplessly for a long moment, not sure what to do. Suddenly he had a flash of intuition. "You're hungry?" The toddler hiccupped and burrowed against his chest.

Without any other ideas, Reg stumbled into the kitchen and picked up the tin of formula he had purchased the day before. Trying to make the bottle and hold Harry at the same time was difficult. Powder was spilled and water sloshed all over the counter. Finally though, he succeeded and held a bottle of the odd smelling mixture up to the toddler. Harry eyed it warily. He nearly growled in frustration as the toddler pushed the bottle away. "Come on. Don't you want to eat?" It took a lot of willpower to keep his voice calm and not throw the bottle on the floor. Regulus was tired and he was definitely not a morning person. He tried giving Harry the bottle again. "No!" The small voice sounded about as frustrated as Reg was feeling. Gritting his teeth, he set the bottle on the counter. "Well I guess you aren't hungry then."

Harry started wailing again as Regulus began walking back towards the crib. "What do you want?!" Harry sniffled and glared accusingly at the sharp tone. Reg closed his eyes and counted to ten. "Okay." He walked back into the kitchen and sorted through the cabinets one handed. There wasn't much. He decided on a box of muggle cereal and carried it over to the table. He sat down with Harry on his lap and shook a little of the cereal onto the tabletop. With a happy little squeal, Harry snatched up a few pieces and shoved them in his mouth. His tiny teeth (he was still missing a few) crunched the cereal merrily. Regulus sighed in relief. "Guess you're too old for bottles then."

After Harry finished his breakfast with a great deal of gusto and slobber, Reg cleaned him up and put him back in his crib. For a moment, he considered going back to sleep but decided on a shower instead. The hot water was heavenly. He felt himself relax and the Harry induced headache that had begun pounding in his temples faded away. He allowed himself a few moments peace, just standing there with his eyes closed, then briskly washed himself. He couldn't leave a toddler alone for too long after all.

Soon enough he was dressed and leaning back over the crib, lifting Harry out again. Harry giggled at him and tangled his little hands in Regulus' still damp hair. "P'foot!" Regulus stopped himself from wincing at the refrence to Sirius. "No, I'm not padfoot. My name is Regulus." Harry cocked his head and stared up at him wide eyed. "Regulus," Reg repeated patiently. "E'lus," Harry repeated, his little face solemn. "Reg-ul-us," Regulus enunciated. Harry beamed, "E'lus!" Regulus sighed. "Close enough Harry."

Harry needed some clothes and toys. At around nine, Regulus bundled the little boy up as best he could in a set of his own robes he had shrunk. Then he carefully transfigured them to look like muggle clothes. Afterall, it wouldn't do to draw attention to themselves. His own outfit consisted of a pair of plain black slacks and a white button up shirt. His cloak he transfigured to a hansom black coat that reached mid-thigh. To be safe, he cast a glamour over himself to make his features a little more rough and he made sure to turn his eyes green like Harry's. No one would recognize him as a Black and with his new eye color, no one would question his relationship with Harry. Hoisting the toddler up, he exited the apartment.

Muggle London had horrified and intimidated Regulus the first time he had roamed it. That had been the night Sirius had died. He had gone to Gringotts, his black robes still bloody, and withdrew most of his money. After converting it to muggle currency, he had stumbled around the dark streets until he came to a rather seedy hotel. The next day he had gone and rented his own apartment and bought some new clothes. He had spent the weeks up 'til Halloween learning about how the muggles lived and trying to track down the Potters. Walking down the street now, he watched Harry look around in innocent wonder. Regulus chuckled. He had of course considered returning to the wizarding world, but since he wasn't Sirius they might legally take Harry away from him. No, living unknown in the muggle world was for the best.

Swallowing his instinctive, pureblood distaste as they came to a small shop advertising children's clothes, Reg adjusted Harry on his hip and walked inside. An hour and two shops later, Harry had a new wardrobe and enough toys to keep him busy (Regulus hoped). They stopped for a bit of lunch. He fed Harry a bowl of soup as every woman in the restaurant giggled and remarked how cute it was. Harry got more of the soup on the table than in his mouth, but Regulus didn't mind as the toddler seemed happy enough.

Their last stop was a real estate agency. A blonde woman with fake eyelashes and too much makeup gushed over Harry and flirted shamelessly with Regulus. Fighting back the "mudblood" and "filthy muggle" comments on the tip of his tongue, he forced a polite smile and looked over the houses available. An hour and a half later, he had picked three properties to go look at during the week and gave the woman his contact information. With a great deal of relief, he left the agency and started back towards his apartment. "Thank Merlin that's over!" Harry looked up at him and seemed to agree, then the green eyes disappeared as he snuggled against Regulus' shoulder. "E'lus," the toddler murmured sleepily. Regulus looked down and tightened his hold, feeling a strange warmth in his chest. "Harry," he said simply and cuddled the small body to him all the way home.


	4. Choices

**November 8, 1981**

Regulus slumped to the floor. He was exhausted and sweaty, his simple black slacks and shirt were filthy with dust and grime. Still, he and Harry were all moved into their new house. He looked around the small two bedroom cottage proudly. He had been so tempted to make the move easier with magic, but he restrained himself. The fear someone would find them hitting him every time he so much as twitched for his wand.

He glanced over at the small playpen he had set up well away from the chaos. Harry had dozed off about a half hour before, the stuffed dog he had been playing with tucked under one arm. Regulus felt his lips twitch up in a tired smile. He lingered another moment on the newly cleaned hardwood floor, before hauling himself up with a groan. _How do muggles do it? _He ran a hand longingly over the hawthorn wand up his sleeve and staggered into the bathroom.

The warm water was heavenly and it was almost painful to turn off the shower and get dressed. Regulus couldn't remember the last time he had done so much physical labor. Actually, he was pretty sure he had never done that much before. Making his way stiffly back to the living room, he paused and checked on Harry. The toddler was awake, and stared up at him happily with his big green eyes.

"Up!" Two chubby arms reached for him and Regulus picked the child up without hesitation. The past week had cured him of all nervousness around Harry and like many new parents, he found routine had ingrained such actions as diaper changes, feedings, and picking the toddler up. He could now do all those things with relative ease, even if it was still a little unusual for him to have so much physical contact with someone else.

Sirius had always been the touchy one. Their parents certainly weren't and the majority of human contact he had gotten had always been from Siri and occasionally one of his schoolmates. Now, he was slowly getting used to Harry clinging around his neck and snuggling into him. To his surprise, Regulus found he didn't really mind. Putting Harry in his highchair, he ruffled the boy's dark hair absent mindedly and got to work on supper.

The evening had gone smoothly despite his tired muscles and dinner and bath time had gone without a problem. As he was putting Harry down in his crib however, a familiar tapping sounded at the windows. Regulus froze, his face paling rapidly. "Probably just the wind," he whispered to the half asleep toddler. Gently tucking Harry in, he pulled his wand and walked silently towards the living room. A cold feeling crept into his chest as he saw a barn owl sitting patiently at the window. Heart in his throat, he let the bird in and accepted it's letter. The owl ruffled it's feathers and flew back outside. He turned his attention back to the letter.

_Regulus Arcturus Black _was inscribed on the outside of the envelope. Reluctantly he raised his wand and checked over the letter for any poison or curses. Finding nothing suspicious, he tucked his wand back in his sleeve and carefully opened the thick parchment. When he unfolded the letter, he almost dropped it. Hands shaking, he sank into a chair and stared at the elegant script in front of him. _The Last Will and Testament of Sirius Orion Black._

An hour later, Regulus was still slumped in the chair. His eyes were irritated and sore from crying, and his chest hurt as he stared blankly at Sirius' will. Siri had left him everything. Everything including Harry, should he and the Potter's be dead. For a briefly stupid moment, Regulus had wondered why Sirius wouldn't have named Lupin as the child's guardian, before remembering that the man was a werewolf. Ah. Regulus had found that out a few years ago by accident. He felt a small twinge of relief. Harry was his now. Legally.

Now he had another issue. Regulus seriously debated on returning to the wizarding world. Yes he had just bought a new house, but since he was now Harry's legal guardian (although only Gringotts would know that until he requested for the documents to be unsealed) he was free to move back if he wanted. Regulus was tempted. The wizarding world was far more familiar, far more comfortable. He was a wizard after all, and Harry was too. But would Harry be safe there?

He knew that not all the death eaters would end up in Azkaban. Would they come after Harry? Well, it was a good possibility. Regulus frowned. Albus Dumbledore would also be a problem. He had seen how the man had subtly manipulated Sirius and his friends. Having been in Slytherin, he knew the man's principals weren't nearly as virtuous and pure as most people seemed to think. A gut feeling, an instinct told him he didn't want Harry anywhere near that man.

Thoughts racing, Regulus lost track of how long he sat in the kitchen. He was somewhat surprised when he heard Harry wake up. Pale pink and golden light filtered in through the windows as he went to get the toddler. He'd decide what to do later. He had time.

**Short but I know I haven't updated in forever. I'm just a bit busy but I haven't given up on any of my stories just yet. Thank you all for being patient and thank you The Fluffy Ball for your review getting me motivated again!**


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